Pressure-regulated diaphragm pump

ABSTRACT

A piston-operated diaphragm pump for pumping liquids containing solids in suspension has a pump chamber divided into primary and secondary sides by a flexible diaphragm reciprocated by hydraulic pressure produced by a piston acting on a clean liquid in the primary side of the chamber. The solids-containing liquid from the secondary side of the pump is delivered via a closed tank to a treatment such as filtration. The clean liquid is circulated through a fluid circuit which includes a throttle valve operated by a rise in pressure in the closed tank, so that if the backpressure of the solids-containing liquid rises above a predetermined level e.g., due to filter blockage, the flow of clean liquid in the fluid circuit is throttled and the amount of clean liquid in the primary side of the pump thereby reduced to effect a corresponding reduction in the delivery rate and pressure of the pump.

United States Patent Stahlkopf Dec. 18, 1973 PRESSURE-'REGULATED DIAPHRAGM PUMP Primary Examiner-Frank A. Spear, Jr. [75] Inventor: Friedrich R. R. Stahlkopf, Buchen, AttorneYF'Rlchard Stevens et Germany 57 ABSTRACT [73] Ass1gnee. gztromthl; Tuchenhagen, Buchen, pistomqp'erateddiaphragm pump for pumping liqu1ds contammg sol1ds 1n suspenslon has a pump cham- [22] Filed: Jan. 17, 1972 ber divided into primary and secondary sides by a flexible diaphragm reciprocated by hydraulic pressure [21] Appl' zlsns produced by a piston acting on a clean liquid in the primary side of the chamber. The solids-containing [30] Foreign Application Priority Data liquid from the secondary side of the pump is deliv- Jam 21, Germany P 21 02 7623 ered via a closed tank to a treatment such as filtration. The clean liquid is circulated through a fluid circuit 52 us. c1....- 210/136, 210/137, 417/395 which includes a throttle valve Operated by a rise in 511 1m. (:1 801d 35/26, BOld 35/14 Pressure in the closed tank. so that if the back- [58] Field of Search 210/136, 137, 257, Pressure of the Solids-containing liquid rises above 210/416; 7 5 predetermined level e.g., due to filter blockage, the flow of clean liquid in the fluid circuit is throttled and [56] References Cited the amount of clean liquid in the primary side of the UNITED STATES PATENTS pump thereby reduced to effect a corresponding reduction in the delivery rate and pressure of the pump. 3,101,058 8/1963 Carr, Jr. et al. 417/395 X 2,430,097 11/1947 Bauer 210/257 x 6 Cl 1 a ng Figure IIIIIIIIIIIIIIIIIIIIIIIIIA PRESSURE-REGULATED DIAPHRAGM PUMlP BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a piston-operated diaphragm pump for pumping liquids containing solids in suspension, and to means for'regulating the delivery rate and pressure of the pump in dependence on the pressure of the solids-containing liquid on the secondary or delivery side of the pump.

2. Description of the Prior Art Piston diaphragm pumps are commonly used for solids-containing liquid such as dirty water, particularly if the liquid has to be conveyed against a high pressure, such as is developed on the inlet side of a filter press. The problem arises with filter presses in which solid matter from the liquid is retained; asthe filter becomes increasingly charged, the pressure in the piston diaphragm pump on the dirty water or secondary side increases and a lower delivery rate is required.

At present, the regulation of the delivery of a piston diaphragm pump is preferably carried out from the clean liquid side i.e., the primary side of the pump.

The pressure of the liquid, e.g. clean water, on the primary side is kept within required limits by for example, a relief pressure valve, so that as the pressure on the secondary side rises, the relief pressure valve on the primary side comes into operation and prevents a further rise in pressure in the pump.

This process of pressure regulation on the primary side using a relief pressure valve has the disadvantage that the water flowing through the valve becomes hot and evaporates. Further another disadvantage of this primary regulation is that the energy from the moving piston has to be destroyed in the relief pressure valve, so that the power requirement at the lowest output of the pump is just as high as when the pump is operating under full load. The present invention provides a means for regulating the pressure and the delivery rate of the pump without the development of heat as a result of the liquid flowing through a valve and so that the power requirement of the pump becomes correspondingly smaller as the output of the pump falls.

This is achieved according to the invention by reducing the quantity of clean liquid in the primary side of the pump by valve means controlled by the pressure of the dirty liquid on the secondary side of the pump. The diaphragm therefore loses its stroke and the pump loses its conveying capacity up to the total zero point.

SUMMARY According to the invention clean liquid circulates through the primary side of the pump via a diaphragmcontrolled valve of known design and through an additional regulating valve which rests directly on a pressure tank on the dirty liquid side.

The diaphragm-controlled valve is able to pass clean liquid into the primary side only via this regulating valve. This regulating valve is pressure-controlled in such a way that at elevated pressure in the dirty liquid pressure tank it throttles or closes the feed to the diaphragm-controlled valve so that the clean liquid side no longer receives a supply of liquid.

The liquid in the clean liquid side is discharged through a throttle valve with each stroke so that as the supply of clean liquid is reduced the convey-ing dis:

phragm is acted upon less and less by the piston; the stroke is reduced, and when a predetermined pressure in the compressed air tank is reached it comes to a standstill so that the pumping ceases.

The throttle valve is always present on the clean water side because as a rule somewhat more liquid is sucked up on the clean water side than is necessary. This excess flows away through the throttle valve.

So that the legal requirements regarding pressure safety of the compressed air tank are fulfilled, a safety valve is also fitted on the clean water side. If, therefore, the mechanical plant on the secondary side should fail, the primary side is safeguarded by a safety valve of known design, so that no excess pressure can occur on the secondary side.

Hitherto the secondary side has been protected by pressure plates which have the great disadvantage that in the event of breakdown the plant comes to a standstill and, more important still, there is an uncontrollable spurting of the dirty liquid.

The dirty liquid side can be protected by a standard valve; in this process an additional safety valve may be provided on the clean liquid side.

This additional safety valve on the clean liquid side is natually dimensioned according to the pressure transmitted from the primary to the secondary side.

BRIEF DESCRIPTION OF THE DRAWING The drawing diagrammatically illustrates a diaphragm pump according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the conveying diaphragm l is located in a known manner between the dirty water or secondary side 2 of the pump chamber and the clean water or primary side 3 of the pump chamber. A cylinder 4 is located in the primary side 3, and this cylinder contains the reciprocating piston S with its piston rod 6. The dirty water to be conveyed enters at A into the suction valve housing 7 through the non-return ball 8, so as to enter the pressure valve housing 9 in a known manner at B. Through the pipe 10, the dirty water enters the compressed air tank 11, and leaves through the pressure pipe 112 at C. In the compressed air tank the dirty water maintains a water level 13. A regulating valve 14 is mounted on the compressed air tank, and includes a regulating seat 17. From this valve regulating seat 17 there extends a suction pipe 18 which leads to a non-return valve 19 having a non-return ball 20. The valve 19 communicates with a diaphragm-controlled valve 22 via a pipe 21.

This diaphragm-controlled valve 22 operates in such a way that the conveying diaphragm l in its suction position 1a opens the valve; this is done by means of a lever 23 pivoted at 24 and connected at 25 to a valve ball 26 which co-operates with a seat 27. When the valve is open clean water can pass through the pipe 28 in a known manner into the clean water side 3 of the pump. When the piston 5 advances in the cylinder 4, the diaphragm is moved into position lb. The excess water sucked up through the pipe 21 and the suction pipe 18 flows through the pipe 29 via a throttle valve 30 having a non-return ball 31 and a pressure spring 32,

A suction pipe'l8a leads into the regulating valve 14.

If the pressure in the compressed air tank 11 increases above a predetermined limit, the control diaphragm 16 is acted upon and closes the control seat 17 so that the suction pipe 18 receives less water; the clean water in the primary side 3 is reduced as at each stroke of the piston water escapes via the pipe 29 into the clean water container 34. The desired pressure in the compressed air tank 11 can be determined by means of the control spring 16.

If for unforeseen reasons the pressure in the compressed air tank 11 should rise above the permissible limit, according to the invention a safety device is provided on the clean water side. This comprises a safety valve 35 with a non-retum ball 36 and a regulating spring 37. This safety valve 35 is connected by a pressure pipe 38 with the clean water side 3 of the pump.

In the event of there being too much pressure in the compressed air tank 11 and an individual part of the apparatus does not function, the safety valve 35 would come into operation and would feed back the excess pressure via the pipe 39 advantageously into the clean water container 34.

By means of this additional safety valve 35 on the clean water side, that is to say on the primary side, the accident regulations relating to the compressed air tank 11 are satisfied, because if the regulating spring 37 is suitably chosen it is no longer possible for excess pressure to occur in the compressed air tank 11. Accordingly, the invention has the important advantage that with the compressed air tank 11 a pressure plate may be dispensed with.

In this apparatus it is immaterial how the regulating valve 14 is designed, because according to the invention this regulating valve rests directly, that is to say without any special pipe or connection, on the compressed air tank 11, so that no deposits of dirt can be formed.

Instead of a regulating diaphragm 15 it is possible to use a piston or the like and instead of the ball valves shown other valves of any suitable type may be used. 1

I claim:

1. A piston-operated diaphragm pump for pumping a liquid containing solids in suspension, comprising a pump body defining a pump chamber, a diaphragm dividing the chamber into a primary side and a secondary side, a piston in the chamber on the primary side operable to reciprocate the diaphragm by hydraulic pressure on clean liquid in the primary side, an inlet and an outlet in the secondary side, through which the solidscontaining liquid is induced to flow by reciprocation of the diaphragm, a closed tank having an inlet for receiving the solids-containing liquid from the pump, an outlet in the tank for said liquid, and means for varying the quantity of clean liquid in the primary side of the pump chamber in dependence on the pressure in said tank.

2. A pump according to claim 1, wherein the primary side of the pump chamber is provided with an inlet and an outlet for clean liquid, and said means for varying the quantity of clean liquid in the primary side comprises a fluid circuit of clean liquid connecting said inlet to said outlet and a regulating valve in said circuit operable to throttle the flow of liquid through said circuit on a rise in pressure in said tank above a predetermined level.

3. A pump according to claim 2, wherein the inlet in the primary side of the pump chamber includes a diaphragm controlled valve operable to allow a flow of clean liquid into the chamber during the suction stroke of the diaphragm.

4. A pump according to claim 3, wherein said fluid circuit includes a container for clean liquid, said container having an inlet and an outlet for said liquid, said inlet incorporating a non-retum valve.

5. A pump according to claim 4, wherein the primary side of the pump is provided with a pressure safety device comprising a second outlet in the primary side which communicates with said clean liquid container through a spring-biassed non-retum valve.

6. A pump according to claim 2, wherein the regulating valve comprises a diaphragm in a wall of the tank operable above a predetermined air pressure in the tank to throttle the flow of fluid in said circuit. 

1. A piston-operated diaphragm pump for pumping a liquid containing solids in suspension, comprising a pump body defining a pump chamber, a diaphragm dividing the chamber into a primary side and a secondary side, a piston in the chamber on the primary side operable to reciprocate the diaphragm by hydraulic pressure on clean liquid in the primary side, an inlet and an outlet in the secondary side, through which the solids-containing liquid is induced to flow by reciprocation of the diaphragm, a closed tank having an inlet for receiving the solids-containing liquid from the pump, an outlet in the tank for said liquid, and means for varying the quantity of clean liquid in the primary side of the pump chamber in dependence on the pressure in said tank.
 2. A pump according to claim 1, wherein the primary side of the pump chamber is provided with an inlet and an outlet for clean liquid, and said means for varying the quantity of clean liquid in the primary side comprises a fluid circuit of clean liquid connecting said inlet to said outlet and a regulating valve in said circuit operable to throttle the flow of liquid through said circuit on a rise in pressure in said tank above a predetermined level.
 3. A pump according to claim 2, wherein the inlet in the primary side of the pump chamber includes a diaphragm controlled valve operable to allow a flow of clean liquid into the chamber during the suction stroke of the diaphragm.
 4. A pump according to claim 3, wherein said fluid circuit includes a container for clean liquid, said container having an inlet and an outlet for said liquid, said inlet incorporating a non-return valve.
 5. A pump according to claim 4, wherein the primary side of the pump is provided with a pressure safety device comprising a second outlet in the primary side whiCh communicates with said clean liquid container through a spring-biassed non-return valve.
 6. A pump according to claim 2, wherein the regulating valve comprises a diaphragm in a wall of the tank operable above a predetermined air pressure in the tank to throttle the flow of fluid in said circuit. 